Seal pattern for ultra-thin liquid crystal display device

ABSTRACT

A seal pattern for a liquid crystal display device includes a substrate having an active area and a non-active area, a main seal pattern arranged in a boundary between the active area and the non-active area and having an injection hole, a V-shaped seal pattern arranged in the non-active area and spaced apart from the injection hole, wherein an open portion of the V-shape faces in a direction opposite the injection hole, and a sub-seal pattern arranged in the non-active area, having a same width as that of the main seal pattern, and having a plurality of exhaust holes arranged in positions corresponding to the V-shaped seal pattern and the injection hole.

This application is a divisional of prior application Ser. No.10/279,116, filed Oct. 24, 2002.

This application claims the benefit of Korean Patent Application No.2001-69110, filed on Nov. 7, 2001 in Korea, which is hereby incorporatedby reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) deviceand more particularly, to a seal pattern for ultra-thin liquid crystaldisplay devices.

2. Discussion of the Related Art

Liquid crystal display (LCD) devices such as active matrix LCDs (AMLCDs) are widely used in devices such as notebook computers, desktopmonitors, etc., due in part to their high resolution and their abilityto display color and moving images. LCD devices generally include anupper substrate (i.e., an array substrate) coupled to, and spaced apartfrom, a lower substrate (i.e., a color filter substrate). A layer ofliquid crystal material is typically disposed between the array andcolor filter substrates. Electrodes are provided on each of the upperand lower substrates such that electrodes of opposing substrates faceeach other. Anisotropic optical properties of the liquid crystalmaterials may be exploited by liquid crystal display devices to produceimages. By varying the orientation of liquid crystal molecules in anelectric field, the transmissivity of light within the layer of liquidcrystal material may be selectively controlled. Liquid crystal displaydevices also include thin film transistors and pixel electrodes arrangedin a matrix pattern.

Fabrication of LCD devices typically involves many processes includingthe formation of an array substrate, formation of a color filtersubstrate, and injection of liquid crystal material between the arrayand color filter substrates. Formation of array substrates includesforming switching elements and pixel electrodes. Formation of colorfilter substrates includes forming color filters and common electrodes.

FIG. 1 illustrates a cross-sectional view of a liquid crystal displaypanel used in a typical LCD device.

Referring to FIG. 1, an upper substrate 10 and a lower substrate 30 arecoupled to, and spaced apart from each other. A layer of liquid crystalmaterial 50 is interposed between the upper and lower substrates 10 and30, respectively. A gate electrode 32 is formed on a transparentsubstrate 1 included within the lower substrate 30 and a gate insulator34 is formed on the gate electrode 32. A semiconductor layer 36,including an active layer 36 a and an ohmic contact layer 36 b, isformed on the gate insulator 34. A source electrode 38 and a drainelectrode 40 are formed on the semiconductor layer 36. A channel region“ch”, including an exposed portion of the active layer 36 a, is formedbetween the source electrode 38 and the drain electrode 40. The gateelectrode 32, the semiconductor layer 36, the source electrode 38, thedrain electrode 40, and the channel “ch” constitute a thin filmtransistor “T”. Though not shown in FIG. 1, a plurality of gate linesare connected to the gate electrode 32 and extend along a firstdirection. Further, a plurality of data lines are connected to thesource electrode 38 and extend along a second direction, perpendicularto the first direction. Crossings of the gate and data lines definespixel regions “P”. A passivation layer 42, including a drain contacthole 44 formed therein, is formed on the thin film transistor “T”. Apixel electrode 48 is formed in the pixel region “P” and is connected tothe drain electrode 40 via the drain contact hole 44. A cell area of thearray substrate includes a connection portion for connecting to anexternal driving circuit. Accordingly, the cell area of the arraysubstrate is wider than a corresponding cell area of the color filtersubstrate. A lower alignment layer 46 is formed on both the passivationlayer 42 and the pixel electrode 48 in order to induce an alignment ofthe liquid crystal material 50. A color filter 14, for filtering lightwithin a specific wavelength range, is formed beneath a transparentsubstrate 1 included within an upper substrate 30 at a positioncorresponding to the pixel electrode 48. A black matrix 12, forprotecting light leakage and for preventing light from contacting thethin film transistor “T”, is formed in boundary areas between each colorportion of the color filter 14. A common electrode 16, serving as anelectrode with which to apply voltage to the layer of liquid crystalmaterial 50, is formed beneath the color filter 14 and the black matrix12. An upper alignment layer 18, similar to the lower alignment layer46, is formed beneath the common electrode 16. A cell gap between theupper and lower substrates 10 and 30, respectively, is sealed using aseal pattern 52. The seal pattern 52 is provided along the edges of thesubstrates to prevent leakage of liquid crystal material 50.Additionally, the seal pattern 52 maintains the upper and lowersubstrates 10 and 30 a predetermined distance from one another (e.g.,maintains the cell gap between the upper and lower substrates 10 and 30,respectively) and enables liquid crystal material to be injected.

As LCD manufacturing technologies progress, LCDs are finding newapplications in lap-top computers, video cameras, aviation instrumentpanels, other electronic devices, etc., the manufacturable size ofsubstrates in LCDs increase, and ways of fabricating LCDs to be thinnerand lighter continue to be evaluated.

Typical glass substrates used in LCDs are about 0.7 mm thick. As thesize of the substrate increases, however, the weight and thickness ofthe substrates must be reduced through chemical (e.g., with the use ofetchants such as hydrofluoric acid) or physical (e.g., grinding,polishing, etc.) material removal processes. Through these materialremoval processes, minimum substrate thicknesses of about 0.5 mm to 0.6mm are attainable upon consideration of factors such as substratebending and external impacts encountered during a high speed revolutionspin coating processes. Physical material removal processes are oftenineffective in maintaining optimal surface roughness and substratethickness. Accordingly, chemical material removal processes may beemployed by dipping LCD substrates in, for example, a hydrofluoric acidsolution.

The fabrication of liquid crystal cells typically includes steps offorming an alignment layer to align liquid crystal molecules, forming acell gap, cutting cells, injecting liquid crystal material, and sealingan injection hole arranged between the substrates.

FIG. 2 illustrates a flow chart of a process used fabricating liquidcrystal cells of ultra-thin liquid crystal display devices. A firstprocess step (ST1) includes cleaning the array and color filtersubstrates by removing particles on the substrate prior to formation ofthe alignment layer on the substrate. A second process step (ST2)includes forming the alignment layer by forming thin polymer film on thesubstrate, hardening, and rubbing the thin polymer film. A third processstep (ST3) includes forming a seal pattern and a spacer. The sealpattern forms a cell gap allowing the injection of liquid crystalmaterial between the substrates and preventing the injected liquidcrystal material from leaking. In ultra-thin liquid crystal displaydevices, the seal pattern also includes a sub-seal pattern forpreventing etchants from infiltrating into the cell gap during any ofthe aforementioned material removal processes. The seal pattern isfabricated using screen-printing technology, thermosetting resin, andglass fiber. The spacer is usually formed on the array substrate anduniformly maintains the gap between the two substrates. The seal patternis typically formed on the color filter substrate to minimize error inattaching the upper and lower substrates. A fourth process step (ST4)includes aligning and attaching the upper and lower substrates to eachother. The degree to which the upper and lower substrates may be alignedis determined by a measuring an alignment margin, usually less than afew microns, provided when the substrates are initially designed. If theupper and lower substrates are aligned and attached with an alignmentmargin larger than a predetermined error margin, the display quality ofthe liquid crystal display device may be deteriorated due to lightleakage during operation of the liquid crystal cell. After the sealpattern is formed on one of the upper or lower substrates, thesubstrates undergo a pre-heating process and are attached together in atemporary fixing process. Subsequently, the substrates are permanentlyattached together using a hardening process (e.g., a thermo-compressionbonding process). A fifth processing step (ST5) includes cutting theattached substrates into a cell unit. A single glass substrate typicallyincludes a plurality of smaller array or color filter substrates in cellareas that need to be separated. A sixth process step (ST6) includesinjecting liquid crystal material into the separated cells. Since eachcell has a cell gap of only a few micrometers per hundreds of squarecentimeters in substrate area, a vacuum injection method, inducing acapillary phenomenon within the cell gap, is typically used in injectingliquid crystal material into the cell. After the liquid crystal materialis injected to the cell, an injection hole through which the liquidcrystal material was injected, is sealed. A seventh processing step(ST7) includes forming an ultra-thin substrate by etching the exteriorsurfaces of the attached substrates. As will be described in greaterdetail below, this etching process includes a cleaning step, an etchingstep, and a drying step. Upon completion of the aforementionedprocessing steps, the liquid crystal display panels are inspected.Subsequently, a polarization film is formed on an outer surface of eachof the substrates and a driving circuit is connected to the substrates.

FIG. 3 illustrates a flow chart of a etching process for formingultra-thin substrates described in step ST7 of FIG. 2.

Referring to FIG. 3, a first processing step (STI) includes removingcontaminations from the exterior surfaces of the attached substrates isperformed before they are etched within an etching apparatus.Contaminations found on the outer surfaces of the attached substratescan cause etching errors and prevent uniform etching of the substrates.Etching errors and non-uniform etching result in a degradation in thequality of images displayable by the liquid crystal display device bydiffusing reflections and refractions at the surface of the attachedsubstrates. Contaminations include organic films or minute particles andmay be removed using cleaning solutions such as IPA (isopropyl alcohol)or DI water (deionized water). After contaminations are removed, thecleaned substrates are arranged within an etching apparatus containingan etchant such as a hydrofluoric acid (HF) solution and are etched fora predetermined amount of time in a second processing step (STII).Subsequently, in third processing step (STIII), any etchant remaining onthe substrates is removed. Finally, in fourth processing step (STIV),the cleaned substrates are dried.

FIG. 4 illustrates a plan view of a seal pattern used in typicalultra-thin liquid crystal display devices.

Referring to FIG. 4, a glass substrate may, for example, include twoliquid crystal cells. The seal pattern of the ultra-thin type liquidcrystal display device includes a main seal pattern 60 a, in which theinjection hole 61 is provided, and a sub-seal pattern 60 b surroundingthe main seal pattern 60 a. The sub-seal pattern 60 b does not containany openings and thereby prevents etchant or cleaning solution frompenetrating into the main seal pattern 60 a.

FIG. 5 illustrates a cross-sectional view along a line V-V shown in FIG.4.

Referring to FIG. 5, air between the main seal pattern 60 a and thesub-seal pattern 60 b is introduced when a substrate 68 is attached.Because the sub-seal pattern 60 b does not include an opening, airbecomes trapped between the substrates and the seal patterns and maycause serious problems. The air trapped between the main seal pattern 60a and the sub-seal pattern 60 b may induce a rupture 64 in the main sealpattern 60 a and produce air bubbles 66 in the sub-seal pattern 60 b.

In order to solve the foregoing problems, Applicants of the presentinvention have disclosed in U.S. patent application Ser. No. 09/737,766,filed Aug. 9, 2001, a seal pattern structure for the ultra-thin liquidcrystal display devices. FIG. 6A illustrates a plan view of the sealpattern structure of the ultra-thin liquid crystal display devicedisclosed in the aforementioned application. A plurality of sealpatterns 82 are formed on the substrate 70 of the liquid crystal cell72.

Referring to FIG. 6A, the seal pattern 82 includes a main seal pattern74 having an injection hole 73, a first sub-seal pattern 76 surroundingthe main seal pattern 74 and a second sub-seal pattern 78 surroundingthe first sub-seal pattern 76 and maintained a predetermined distancefrom an edge of the substrate 70. The first and second sub-seal patterns76 and 78, respectively, include at least one opening, VIa. A thirdsub-seal pattern 80 is formed between the first and second sub-sealpatterns 76 and 78, respectively, adjacent the at least one opening VIaof the second sub-seal pattern 78.

FIG. 6B illustrates a magnified view of area “VIb” shown in FIG. 6Aincluding an exhaust path taken by air during the thermo compressionbonding process.

Referring to FIG. 6B, when the air is exhausted from the liquid crystalcell 72 during the thermo compression bonding process, a bottleneckphenomenon occurs and a high air pressure is concentrated at theinjection hole 73. However, the exhaust path defined by the seal patternshown in FIG. 6B is also long and tortuous. Accordingly, the exhaustpath shown in FIG. 6B is inefficient in facilitating the transport ofair and contributes to the generation of highly pressurized air atinjection hole 73. The high air pressure weakens the adhesive strengthof the sealant at the injection hole 73 and increases the likelihood ofcell gap errors. Furthermore, alignment spots, capable of preventingcertain pre-tilt angles from being imparted to the liquid crystalmaterial, may be generated in a portion of the alignment layers locatednear the injection hole 73 as a result of the high air pressure.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a seal patternstructure of an ultra-thin liquid crystal display device thatsubstantially obviates one or more of problems due to limitations anddisadvantages of the related art.

An advantage of the present invention provides a seal pattern structurefor a liquid crystal display device (e.g., an ultra-thin LCD device)allowing air introduced during an attaching process to be efficientlyexhausted from a liquid crystal cell while preventing etchant frompenetrating into the liquid crystal cell.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a sealpattern for a liquid crystal display device including a substrate withan active area and a non-active area includes a main seal patternarranged in a boundary between the active and non-active areas andhaving an injection hole, a V-shaped seal pattern arranged in thenon-active area, spaced apart from the injection hole, wherein an openportion of the V-shape faces in a direction opposite the injection hole,and a sub-seal pattern arranged in the non-active area, having a samewidth as that of the main seal pattern, and having a plurality ofexhaust holes arranged in positions corresponding to the V-shaped sealpattern and the injection hole.

In one aspect of the present invention, the injection hole of the mainseal pattern may include a plurality of injection hole dams that arespaced apart from each other.

In another aspect of the present invention, a thickness of the substratemay be between about 0.3 mm and about 0.6 mm.

In yet another aspect of the present invention, the sub-seal pattern mayfurther include an oblique seal pattern arranged at sides of theV-shaped seal pattern wherein a distance between lower ends of theoblique seal pattern corresponds to a width of the injection hole. Inone aspect of the present invention, the oblique seal pattern mayinclude at least two members obliquely oriented towards each other.

In still another aspect of the present invention, the sub-seal patternmay further include a cell-support sub-seal pattern formed parallel toan upper portion of the main seal pattern. The cell-support sub-sealpattern may include side portions arranged to correspond with diagonalpaths formed between the injection hole and the exhaust holes.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 illustrates a schematic cross-sectional view of a liquid crystaldisplay panel used in a liquid crystal display device;

FIG. 2 illustrates a flow chart of a process used in fabricating anultra-thin liquid crystal display device;

FIG. 3 illustrates a flow chart of a process corresponding to step ST7as shown in FIG. 2;

FIG. 4 illustrates a plan view of a seal pattern for use in ultra-thinliquid crystal display devices;

FIG. 5 illustrates a cross-sectional view taken along a line V—V asshown in FIG. 4;

FIG. 6A illustrates a plan view of a seal pattern structure of anultra-thin liquid crystal display device;

FIG. 6B illustrates an expanded view of area “VIb” as shown in FIG. 6A;and

FIG. 7 illustrates a plan view of a seal pattern for a liquid crystalcell according to one aspect of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the illustrated embodiment ofthe present invention, which is illustrated in the accompanyingdrawings.

FIG. 7 illustrates a plan view of a seal pattern structure for a liquidcrystal cell (e.g., an ultra-thin liquid crystal cell) according to oneaspect of the present invention.

Referring to FIG. 7, the seal pattern according to the principles of thepresent invention may generally be formed on an attached substratefabricated, for example, according to the processes outlined in FIG. 2.The attached substrate 110 may, for example, include an active area IVaand a non-active area IVb. In one aspect of the present invention, amain seal pattern 164 may be arranged in a boundary between the activearea IVa and non-active area IVb. The main seal pattern 164 may, forexample, include an injection hole 162. A plurality of injection holedams 161 may be formed proximate the injection hole 162 (e.g., withinthe injection hole 162). In one aspect of the present invention theinjection hole dams 161 may be arranged so as to be substantiallysymmetric about the center line of the injection hole 162. The injectionhole dams 161 may serve to maintain uniformity of a cell gap at portionsof a liquid crystal display panel where the main seal pattern 164 is notformed. The injection hole dams 161 may further prevent injected liquidcrystal material from being exposed by the atmosphere. In one aspect ofthe present invention, the plurality of injection hole dams 161 may beformed such that they are spaced apart from each other.

In one aspect of the present invention, a sub-seal pattern 172 may beformed in the non-active area IVb, opposite the injection hole 162. Thesub-seal pattern 172 may have substantially the same width as the mainseal pattern 164 and also be formed to enclose the non-active area IVb.A plurality of exhaust holes 168 may be formed in an outer portion ofthe sub-seal pattern 172.

A first sub-seal pattern 170 may, for example, be formed within thesub-seal pattern 172 and opposite the injection hole 162. A secondsub-seal pattern 166 may, for example, be formed within the sub-sealpattern 172 and at opposite sides of the first sub-seal pattern 170. Inone aspect of the present invention, the first and second sub-sealpatterns, 170 and 166, respectively, may support the substrates of theliquid crystal cell.

Referring still to FIG. 7, the sub-seal pattern 172 may include a firstexhaust hole 168 a, arranged in a position corresponding to theinjection hole 162, and at least two second exhaust hole 168 b spacedapart from the first exhaust hole 168 a by a predetermined distance. Thefirst sub-seal pattern 170 may include a first pattern 170 a, which issubstantially V-shaped. In one aspect of the present invention, thefirst pattern 170 a may be substantially symmetric with respect to thecenter line of the injection hole 162. The first sub-seal pattern 170may further include a second pattern 170 b that may also besubstantially symmetric with respect to the center line of the injectionhole 162. In one aspect of the present invention, the first sub-sealpattern 170 may be substantially symmetric about the center line of thefirst exhaust hole 168 a.

Dotted arrow lines illustrate the internal exhaust path of air exitingthe liquid crystal display panel. The second sub-seal pattern 166 may beformed within the sub-seal pattern 172 and include at least two groupsof at least two members provided outside a region found between theinjection hole 162 and each of the at least two second exhaust holes 168b. Formed in such a manner, the second sub-seal pattern 166 mayfacilitate the transport between the injection hole 162 and the at leasttwo second exhaust holes 168 b out of the liquid crystal display panel.Accordingly, members of the at least two groups included within thesecond sub-seal pattern 166 that are closest to predeterminedcorresponding ones of the at least two second exhaust holes 168 b may beformed so as to be shorter than members of the at least two groupsincluded within the second sub-seal pattern 166 that are farthest awayfrom the predetermined corresponding one of the at least two secondexhaust holes 168 b. Since no portions of the first or second sub-sealpattern 170 or 166, respectively, exists between the injection hole 162and the exhaust hole 168, an unobstructed exhaust path may be providedto air being exhausted from within the liquid crystal display panel.Furthermore, generation of the deleterious alignment spots may beavoided using the seal pattern structure of the present invention.

According to the principles of the present invention, the aforementionedseal pattern need not necessarily be confined to the structure describedherein but may be altered without departing from the scope of thepresent invention.

A material removal process for forming the liquid crystal displaydevices (e.g., ultra-thin liquid crystal display devices) using theaforementioned seal pattern structure will now be explained.

An ultra-thin substrate having a thickness of, for example, betweenabout 0.3 mm and about 0.6 mm may be formed by dipping a liquid crystaldisplay panel including the aforementioned seal pattern structure intoan etchant containing, for example, hydrofluoric acid (HF). In oneaspect of the present invention, a concentration of hydrofluoric acid(HF) within the etchant may be below about 50%, for example, betweenabout 16% and about 17%. In another aspect of the present invention, anetching time may span a in range between about 30 seconds and about 120seconds.

In accordance with the principles of the present invention, an etchingprocess used in forming ultra-thin substrates may be executed between,for example, the attachment (ST4) and cell cutting (ST5) processes asoutlined in FIG. 2. Use of the seal pattern structure illustrated inFIG. 7 allows air introduced during the attachment process to beefficiently exhausted from the liquid crystal display panel whilepreventing etchant from penetrating into the cell during the etchingprocess. The sub-seal pattern may be cut away in a process similar tothat as described with reference to step (ST5) shown in FIG. 2.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the fabrication andapplication of the present invention without departing from the spiritor scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

1. A material removal process for forming a liquid crystal displaydevice, comprising: providing a substrate, the substrate including firstand second regions; providing a main seal pattern in a boundary betweenthe first and second regions, the main seal pattern having an injectionhole; providing a V-shaped seal pattern in the second region and spacedapart from the injection hole, the V-shaped seal pattern having an openportion facing a direction opposite the injection hole; providing asub-seal pattern in the second region, the sub-seal pattern including anexhaust hole through which air is exhausted, the location of the exhausthole corresponding to a location of the injection hole; removing aportion of the substrate; and separating the first region from thesecond region.
 2. The material removal process according to claim 1,wherein the removing comprises etching the substrate in an etchant. 3.The material removal process according to claim 2, wherein the etchantcomprises hydrofluoric acid.
 4. The material removal process accordingto claim 2, wherein the concentration of hydrofluoric acid is belowabout 50%.
 5. The material removal process according to claim 2, whereinthe concentration of hydrofluoric acid is between about 16% and about17%.
 6. The material removal process according to claim 2, wherein theetching is performed between about 30 seconds and about 120 seconds. 7.The material removal process according to claim 1, wherein, after theremoving, the substrate has a thickness of about 0.3 mm to about 0.6 mm.8. The material removal process according to claim 1, wherein the firstregion includes a display region and the second region includes anon-display region.